frandom.c

#include "shadylib.h"

#define m 16777216 /* 2^24: 24 digits are 0 */
#define m1 4096 /* 2^12 */

static t_class *frandom_class;

typedef struct _frandom {
    t_object x_obj;
    t_float x_range;
    unsigned int x_state; //current state (int)
} t_frandom;

static void frandom_seed(t_frandom *x, t_floatarg seed) {
    unsigned int modman = seed;
    x->x_state = modman&(m - 1);
}

static void frandom_bang(t_frandom *x) {
    unsigned int state = x->x_state;

    state = randlcm(state);
    x->x_state = state;
    outlet_float(x->x_obj.ob_outlet, state*x->x_range/16777215.0f);
}

// b = 4103221
static int frandom_makeseed(void) {
    unsigned int p1, p0;
    static unsigned int nextseed = 13458715;

    p1 = nextseed/m1; p0 = nextseed&(m1 - 1);
    nextseed = (((p0*1001 + p1*3125)&(m1 - 1))*m1 + p0*3125)&(m - 1);
    return nextseed;
}

static void *frandom_new(t_symbol* SHADYLIB_UNUSED(s), int argc, t_atom *argv) {
    unsigned int state;
    t_frandom *x = (t_frandom *)pd_new(frandom_class);

    switch(argc) {
        default:
            state = atom_getint(argv + 1);
        case 1:
            x->x_range = atom_getfloat(argv);
        case 0:;
    }
    switch(argc) {
        case 0:
            x->x_range = 1.0;
        case 1:
            state = frandom_makeseed();
        default:;
    }
    floatinlet_new(&x->x_obj, &x->x_range);
    outlet_new(&x->x_obj, &s_float);
    state %= m;
    x->x_state = state;
    return (x);
}

void frandom_setup(void) {
    frandom_class = class_new(gensym("frandom"), (t_newmethod)frandom_new, 0,
        sizeof(t_frandom), CLASS_DEFAULT, A_GIMME, 0);
    class_addmethod(frandom_class, (t_method)frandom_seed, gensym("seed"), A_DEFFLOAT, 0);
    class_addbang(frandom_class, frandom_bang);
}